Electrical and structural properties of BiFeO₃ thin films with four distinct buffer layers: La₂O₃, Pr₂O₃, Sm₂O₃, and Tm₂O₃

In this study, BiFeO₃ thin films were fabricated using a spin-coating technique on SrRuO₃/n⁺-Si substrates, employing four different RE₂O₃ (La₂O₃, Pr₂O₃, Sm₂O₃, and Tm₂O₃) buffer layers. The investigation focused on assessing the structural and ferroelectric characteristics of these films. X-ray diffraction analysis revealed a (110) preferred orientation with a perovskite-rhombohedral structure in films with RE₂O₃ buffer layers. Atomic force microscopy analysis indicated smooth surfaces for these layers. Secondary ion mass spectrometry demonstrated high levels of Bi ions in films with RE₂O₃ buffer layers, while X-ray photoelectron spectroscopy revealed a low Fe²⁺/Fe³⁺ ratio in these layers. Notably, the film with a Sm₂O₃ buffer layer showed a lower leakage current (2.05 × 10⁻⁶ A/cm²) and a higher remnant polarization (43.65 μC/cm²). This improvement is attributed to Sm³⁺ ions fostering (110) orientation, reducing surface roughness, increasing Fe³⁺ content, thereby minimizing oxygen vacancies, and suppressing Fe³⁺ to Fe²⁺ valence fluctuation.